Device for low-frequency communication by magnetic coupling

Abstract

The invention relates to a device for low-frequency communication by magnetic coupling of the type comprising a magnetic field emitter and a receiver placed in an identification member, one of either the emitter or the receiver being furnished with a loop antenna, in which the other of either the emitter or the receiver is constituted by the association of three coils ( 1, 2, 3 ) wound around three perpendicular axes (Ox, Oy, Oz) defining a trihedral so as to obtain an omnidirectional magnetic field by supplying said coils with currents of like frequency.

What is claimed is:  
     
       1. A device for low-frequency communication by magnetic coupling, comprising: 
       an emitter placed in a vehicle; and  
       a receiver placed in an identification member, wherein one of the emitter or the receiver includes a loop antenna, the other of the emitter or the receiver includes three associated coils wound around three perpendicular axes defining a trihedral and creating an omnidirectional magnetic field, and the three associated coils are supplied with currents of like frequency, 60 degrees or 120 degrees out of phase relative to each other.  
     
     
       2. A device according to  claim 1 , wherein the three associated coils are wound on one another around six faces of a parallelepiped, common core. 
     
     
       3. A device according to  claim 2 , wherein the three associated coils are wound on one another around six faces of a core comprising a parallelepiped lamina, a first associated coil being wound breadthwise around a middle portion of the core, a second associated coil being wound around two longest faces of the core, and a third associated coil being wound around edges of the core. 
     
     
       4. A device according to  claim 1 , wherein the three associated coils are wound on two separate cores, a first core having approximately a cubic shape and a second core having a lamina shape of relatively small thickness, one of the three associated coils being wound around edges of the second core, and the other two associated coils being crossed at 90 degrees around the first core. 
     
     
       5. A device according to  claim 1 , wherein the emitter includes the three associated coils, and the receiver includes the loop antenna. 
     
     
       6. A device according to  claim 1 , wherein the emitter includes the loop antenna, and the receiver includes the three associated coils. 
     
     
       7. A device according to  claim 1 , wherein the identification member and its antenna are substantially planar. 
     
     
       8. A device according to  claim 2 , wherein the core comprises a magnetic material. 
     
     
       9. A device according to  claim 1 , wherein the emitter includes the three associated coils disposed on a common spherical core. 
     
     
       10. A device according to  claim 2 , wherein the emitter includes the three associated coils, and the core comprises recesses for positioning and housing the three associated coils. 
     
     
       11. A device according to  claim 2 , wherein the emitter includes the three associated coils, and the receiver includes the loop antenna. 
     
     
       12. A device according to  claim 3 , wherein the emitter includes the three associated coils, and the receiver includes the loop antenna. 
     
     
       13. A device according to  claim 4 , wherein the emitter includes the three associated coils, and the receiver includes the loop antenna. 
     
     
       14. A device according to  claim 2 , wherein the emitter includes the loop antenna, and the receiver includes the three associated coils. 
     
     
       15. A device according to  claim 3 , wherein the emitter includes the loop antenna, and the receiver includes the three associated coils. 
     
     
       16. A device according to  claim 4 , wherein the emitter includes the loop antenna, and the receiver includes the three associated coils. 
     
     
       17. A device according to  claim 2 , wherein the identification member and its antenna are substantially planar. 
     
     
       18. A device according to  claim 3 , wherein the identification member and its antenna are substantially planar. 
     
     
       19. A device according to  claim 4 , wherein the identification member and its antenna are substantially planar. 
     
     
       20. A device according to  claim 5 , wherein the identification member and its antenna are substantially planar.